Chapter 3.1-3.3

Question 1

What is the simplest example of nervous system activity?

Answer 1

Reflex

Question 2

Receiving info is the _________ function of the NS, carried out by the __________

Answer 2

sensory, PNS

Question 3

Processing info is the ____________ function of the NS, carried out by the _______

Answer 3

integrative, CNS

Question 4

Acting on info is a _______ function carried out by the _______

Answer 4

motor, PNS

Question 5

Describe the muscle stretch reflex

Answer 5

Sensory neuron detects stretch, transmits info down its long dendrites and axons to the motor neuron cell body in the spinal chord, motor synapse with muscle stretched to cause contraction

Question 6

Monosynaptic reflex arc

Answer 6

Involves 2 neurons and 1 synapse

Question 7

How does quadriceps contract and hamstring relax when patellar tendon is stretched?
muscle stretch reflex

Answer 7

Sensory neuron stimulated by stretch, 2 things happen. 1. a motor neuron leading to quadriceps motor neuron is stimulated, causing the quadriceps to contract
2. sensory neuron also synapses with an inhibitory interneuron （ short neuron which forms an inhibitory synapse with motor neuron innervating the hamstring muscle), therefore the hamstring relaxes when the patellar tendon.

Question 8

Give an example of reciprocal inhibition.

Answer 8

Concurrent relaxation of the hamstring and contraction of the quadriceps upon stimulation of the sensory neuron.

Question 9

If a reflex occurs without the involvement of the brain, how are we aware of the brain?

Answer 9

1. Sensory neuron also branches to form a synapse with a neuron leading to the brain. 2. other sensory action is received after the action is taken.

Question 10

Basic functional and structural unit of the nervous system

Answer 10

Neuron

Question 11

Bipolar neurons

Answer 11

Neurons with one dendrite

Question 12

Multipolar neurons

Answer 12

Neurons with multiple dendrites

Question 13

Resting membrane potential

Answer 13

Electric potential across the plasma membrane of approximately -70 mV, with the interior of the cell negatively charged with respect to the exterior of the cell.

Question 14

Na+/K+ ATPase

Answer 14

Pumps 3Na+ out of the cell and 2K+ in to the cell w/ the hydrolysis of 1 ATP m/c

Question 15

What is the result of Na+/K+ ATPase?

Answer 15

A sodium gradient with high Na out of the cell and a K+ gradient with high K+ inside the cell.

Question 16

Leak channels

Answer 16

Channels that are open all the time and allow specific ions to leak across the membrane according to their gradient.

Question 17

What is the ratio of K+ leak to Na+ leak

Answer 17

100:1 ; membrane is virtually impermeable to sodium

Question 18

Are neurons the only cells with a resting membrane potential?

Answer 18

No. All cells have a resting membrane potential. Neurons and muscle tissue are unique in using the membrane potential to generate action potentials.

Question 19

If the K+ leak channels are blocked , what will happen to the membrane potential?

Answer 19

Flow of K+ out of the cell makes the cell interior more negatively charged. Blocking K+ leak channels would reduce the magnitude of the resting membrane potential, making the interior of the cell less negative.

Question 20

What would happen to the membrane potential if sodium ions were allowed to flow down their concentration gradient?

Answer 20

Sodium ions are positively charged, if they are allowed to flow down the concentration gradient into the cell, making the interior of the cell less negative and even relatively positive is enough ions flow into the cell.

Question 21

Why can cells be described as polarized

Answer 21

The resting membrane potential establishes a negative charge along the interior of axons ( along the rest of the neuronal interior), the cells r negative on the inside and positive on the outside.

Question 22

Depolarization

Answer 22

Change in the membrane potential frodm the resting membrane potential of approximately -70 mV to less a negative , or even positive potential.

Question 23

Repolarization

Answer 23

Returns the membrane potential to normal.

Question 24

What causes the change in membrane potential ?

Answer 24

Movement of ions into and out of the neurons through ion channels.

Question 25

What do voltage-gated sodium channels do?

Answer 25

In response to change in membrane potential, ions channels open to allow sodium ions to flow down gradient into the cell and depolarize that section of the membrane.

Question 26

What is the effect of opening the voltage-gated sodium channels on the membrane potential?

Answer 26

Sodium ( positively charged) flows into the cell, down its concentration gradient , making the interior of the cell less negatively charged/ even positively charged.

Question 27

If an action potential starts at one end of an axon , will it run out of energy and not reach the other end of the axon?

Answer 27

No, it cannot. Action potentials are continually renewed at each point in the axon as they travel. Assuming there r enough voltage-gated channels , once an action potential, starts, it will propagate without a change in amplitude (size) until it reaches a synapse.

Question 28

Which can cause the interior of neuron to have a momentary positive charge?
A. Open K+ leak channels
B. Activity of Na+/K+ ATPase
C. Opening of voltage-gated sodium channels
D. Opening of voltage-gated K channels

Answer 28

C. Choices A, B and D all make the interior of the neuron more negatively charged.

Question 29

Given the above description, which of the following best describes the response of voltage gated sodium channels to a membrane depolarization from -70mV to -60mV?
A. All of the channels open fully
B. 50%  of channels open fully
C. All of the channels open 50%
D. None of the channels open

Answer 29

Voltage gated Na channels require threshold depolarization to open. A depolarization below the threshold potential will produce no response, while a depolarization greater than or equal to the threshold will cause all of the channels to open fully. This is called an all or none response. The correct answer is D. The depolarization is less than the threshold , so there is no response.

Question 30

Describe how voltage gated Na channels contribute to repolarizing the membrane potential

Answer 30

1) Voltage gated Na channels inactivate very quickly after they open, shutting off the flow of Na+ into the cell. The channels remain inactivated until the membrane potential nears resting values.

Question 31

If a toxin prevents voltage gated Na+ channels from closing, which of the following will occur?
1. Voltage gated K+ channels will open but not close
2. The membrane will not repolarize to the normal resting membrane potential.
3. The Na+/K+ ATPase will be inactivated.
A) 1 only B) 2 only C) 1 and 2 only D) 2 and 3 only

Answer 31

1 is true. Voltage gated K+ channels are normally closed by the repolarization of the mem so if the mem is not repolarized, they will not close. 2 is true. Na+ ions will continue to flow into the cell even as Na+/K+ ATPase works to pump them out. This will prevent repolarization of the membrane. 3 is false. Na+/K+ ATPase will work harder than ever. Therefore, the answer is C.

Question 32

Myelin

Answer 32

Insulating sheath many neurons are wrapped in

Question 33

Glia cells which create the myelin sheaths in PNS and CNS.

Answer 33

PNS: Schwann cells
CNS: Oligodendrocytes

Question 34

Would an axon be able to conduct action potentials if the entire length was wrapped in myelin?

Answer 34

No. Action potential requires movement of ions across the plasma mem to create a wave of depolarization and no ions can enter or exit a neuron where the axonal membrane is covered with myelin.

Question 35

What is another name for the cell body of a neuron?

Answer 35

Soma

Question 36

What is special about the parts of the axon which are wrapped in myelin?

Answer 36

There is no membrane depolarization and no voltage gated sodium channels in these regions.

Question 37

What are nodes of ranvier?

Answer 37

Periodic gaps in the myelin sheath which allow for the passage of ions to occur. Voltage gated Na+ channels and K+ channels are concentrated in nodes of Ranvier in myelinated axons.

Question 38

What effect does myelin sheath have on the movement of potentials?

Answer 38

Myelin sheath dramatically speeds up the movement of action potentials by forcing action potentials to jump from node to node.

Question 39

Saltatory conduction

Answer 39

rapid jumping conduction in myelinated axon

Question 40

Which one of the following is true concerning myelinated and unmyelinated axons?
A) The amount of E consumed by the Na+/K+ ATPase is much less in myelinated axons than in unmyelinated axons .
B) Myelinated axons can conduct many more action potentials per second than can unmyelinated axons
C) The size of action potential depolarization is much greater in myelinated axons than in unmyelinated axons.
D) Voltage gated potassium channels do not play a role in repolarization in unmyelinated axons

Answer 40

Since the A of mem that is conducting is much less in myelinated axons, Na+/K+ ATPase only works to maintain the resting potential in the nodes of Ranvier , whereas in unmyelinated axons the Na+/K+ ATPase hydrolyzes ATP to maintain the resting potential across the entire membrane.( Choice A is correct) The length of the refractory period ( and hence the frequency of action potentials ) is based on the characteristics of the voltage gated Na and K channels , which do not change (choice B is false). The size of depolarization in an action potential does not vary greatly; action potentials are an all or nothing response ( choice C is false). Voltage gated K channels are same in both neurons (choice D is false).

Question 41

Equilibrium potential

Answer 41

Membrane potential where the driving force ( gradient) does not exist. In other words, there would be no net movement of ions across the membrane.

Question 42

What is the equilibrium potential for Na+ and what does this mean regarding ion movements?

Answer 42

Na+ eq.m potential is positive 50 mV. Na+ are driven inward by the concentration gradient. However, if the inside of the cell is too positive, the positively charged ions are repelled, which means that the electrical gradient would drive sodium out. Both of these forces the chemical gradient driving sodium in and the electrical gradient driving sodium out balance eac other at about +50 mV.

Question 43

Glial cells

Answer 43

Specialized, non-neuronal cells that typically provide structural and metabolic support to neurons. They maintain resting membrane potential but do not generate action potentials.

Question 44

List the location and primary function of

Schwann cells

Answer 44

Schwann (PNS): form myelin- increase speed of conduction of action potentials along axon

Question 45

What is the equilibrium potential for K+

Answer 45

K+ has a negative equilibrium potential.

Question 46

Nernst Equation and what it is used to do

Answer 46

E= (RT/zF) ln ( X outside/ X inside)
where E is the equilibrium potential for the ion, R is the universal gas constant, T is the temperature in Kelvin, z is the valence of the ion, F is faraday’s constant and X is the concentration of the ion on each side of the membrane to create a chemical gradient. The relative concentration of the ion on each side of the membrane create the chemical gradient, while the valence ( charge of the ion) helps determine the electrical gradient. The equilibrium potential for any ion is based on the electrochemical gradient for that ion across the membrane.

Question 47

What is the resting membrane potential and what does this reflect regarding the number of each relative channels?

Answer 47

The resting membrane potential is -70 mV. If the cell was completely permeable for K+, the resting potential would be around -90 mV. The fact that the resting potential is very close to the K+ eq. m potential indicates that there are a large number of K+ leak channels in the membrane; the cell at rest is almost completely permeable to K+. The resting potential is slightly more positive than the resting potential of K+, therefore there are a few Na+ leak channels in the membrane. When the membrane does become completely permeable to Na+ at the beginning of the action potential, the membrane shoots up to +35 mV.

Question 48

What is the effect of the passage of one action potential on the membrane?

Answer 48

The passage of one action potential makes the neuron nonresponsive to membrane depolarization and unable to transmit another action potential or refractory, for a short period of time.

Question 49

Absolute refractory period

Answer 49

During this period, a neuron will not fire another action potential no matter how strong a membrane depolarization is induced.

Question 50

Relative refractory period

Answer 50

During this period, neuron can be induced to transmit an action potential, but the depolarization required is greater than normal because the membrane is hyperpolarized.

Question 51

If a fruit fly mutant is found that it has voltage gated K channels that shut more quickly after repolarization, how would this affect the refractory period in the fly?

Answer 51

The absolute refractory period would not be altered, since this is due to the inability of voltage gated sodium channels to open. However, the relative refractory period would decrease.

Question 52

Describe the functions of the following:
Dendrites
Axon
Axon Terminal

Answer 52

Dendrites: receives signals from neighboring neurons
Axon: transmit signals over a distance
Axon terminal: transmits signals to neuron dendrites and tissues

Question 53

Synapse

Answer 53

Junction between the axon terminus of a neuron and dendrites , soma or axon of a second neuron. It can also be the junction between the axon terminus and an organ

Question 54

Electrical synapses

Answer 54

Occur when the cytoplasms of two cells are joined by gap junctions. When 2 cells are joined by these, an action potential can spread directly from 1 cell to the other. Not common in the nervous system although they are quite important in propagating action potentials in smooth and cardiac muscle.

Question 55

Chemical synapses

Answer 55

Found at ends of axons where they meet their target cells: action potential is converted into a chemical signal.

Question 56

Steps involved in the transmission of a signal across a chemical synapse in the nervous system as well as at the junction of neurons with other cell types, such as skeletal muscle cells.

Answer 56

1. An action potential reached the end of an axon, the synaptic knob
   2) Depolarization of the presynaptic membrane opens voltage gated Ca channels
2. Ca influx into the presynaptic cell causes exocytosis of neurotransmitter stored in secretory vesicles.
3. Neurotransmitter molecules diffuses across the narrow synaptic cleft ( small space between cells).
4. Neurotransmitter binds to receptor proteins in the postsynaptic membrane. These receptors are ligand gated ion channels.
5. The opening of these ion channels in the postsynaptic cell alters the membrane polarization.
6. If the membrane depolarization of the postsynaptic cell reaches the threshold of voltage gated sodium channels, an action potentials is initiated.
7. Neurotransmitter in the synaptic cleft is degraded and or removed to terminate the signal.

Question 57

Neuromuscular junction

Answer 57

Chemical synapse that is commonly used
Junction between neurons and skeletal muscle
The neurotransmitter that is released at the neuromuscular junction is acetylcholine. When an action potential reaches a synapse, ACh is released into the synaptic cleft.The ACh binds to its receptor, the receptor opens its associate Na channel, allowing Na to flow down a gradient into the cell, depolarizing the postsynaptic cell membrane. Meanwhile, the ACh in the synaptic cleft is degraded by the enzyme acetylcholinesterase (AChE).

Question 58

A Typical Synapse

Pre and Post synaptic neuron

Answer 58

Presynaptic neuron
1. Voltage gated Ca channels open
2. Influx of Ca
3. Exocytosis of secretory vesicle
4. Release of neuro into synaptic cleft
Postsynaptic neuron
1. Neurotransmitter binds to ligand gated ion channels
2. Ions enter postsynaptic cell
3. Membrane polarization is increased or decreased.

Question 59

Other neurotransmitters

Answer 59

gamma aminobutryric acid GABA
serotonin
dopamine
norepinephrine

Question 60

Excitatory neurotransmitters

Answer 60

A neurotransmitter which opens a channel and depolarizes the postsynaptic membrane. Example ACh

Question 61

Inhibitory neurotransmitters

Answer 61

Neurotransmitters which induce hyperpolarization of postsynaptic membrane. Hyperpolarization is making the postsynaptic membrane potential more negative than the resting potential.

Question 62

What determines the effect on the postsynaptic cell?

Answer 62

The receptor for the neurotransmitter and its associated ion channel. It is not the neurotransmitter which determines the effect on the postsynaptic cell.

Question 63

Do neurotransmitters have fixed properties as an inhibitory or an excitatory neurotransmitter?

Answer 63

No , the same neuro can be excitatory in some cases and inhibitory in others.

Question 64

If a neuro causes entry of Cl- into the post cell, is the neurotransmitter excitatory or inhibitory?

Answer 64

Chloride ions are negatively charged. The entry of Cl into the cell will make the postsynaptic potential more negative or hyperpolarized, so the neuro is inhibitory.

Question 65

If an inhibitor of acetylcholinesterase is added to a neuromuscular junction, then the post membrane will:
A) be depolarized by action potentials more frequently
B) be depolarized longer with each action potential
C) be resistant to depolarization
D) spontaneously depolarize

Answer 65

B is the correct answer. If AChE is inhibited, ACh remains in the synaptic cleft longer, and ACh gated sodium channels remain open longer with each action potential that reaches the synapse. If the Na channels are open longer, the depolarization of the postsynaptic membrane will last longer.

Question 66

Signals can be sent in only one direction through synapses such as neuromuscular junction. Which of the following best explains unidirectional signaling at synapses between neurons?
A) Neuro is always degraded by postsynaptic cell or in the synaptic cleft
B) Only the pre cell has vesicles of neuro
C) Axons can propagate action potentials in only 1 direction
D) Only the post cell has a resting membrane potential

Answer 66

Signalling is unidirectional because only pre cell has vesicles of neuro that are released in response to action potentials and only post neuron has receptors that bind neuro to either depolarize or hyperpolarize the cell. B is correct. Degradation of neuro is irrelevant to the direction of signal propogation ( A is wrong), axons are capable of propagating action potentials in both directions ( although this is not what they normally do) therefore C is wrong and all cells have a resting membrane potential D is wrong.

Question 67

Does magnitude of depolarization vary from 1 action potential to another?

Answer 67

No

Question 68

What is the key regulated step in the nervous system?

Answer 68

Whether or not the neuron will fire an action potential

Question 69

How are action potentials initiated and is it possible to initiate depolarization as a result of a neurotransmitter by 1 action potential?

Answer 69

Action potentials are initiated when the postsynaptic membrane reaches threshold depolarization ( about -50 mV) required to open voltage gated Na channels . The depolarization caused by the release of a neurotransmitter by 1 action potential is not generally sufficient to induce this degree of depolarization.

Question 70

Summation and decision whether to fire an action potential or not

Answer 70

Decision by post whether to fire an action potential or not can be determined by adding effect of all synapses impinging on neuron, both excitatory and inhibitory.
Summation is the addition of stimuli

Question 71

Excitatory postsynaptic potentials

Inhibitory postsynaptic potentials

Answer 71

EPSPs otherwise known as postsynaptic depolarization are caused by excitatory neuro
IPSPs are caused by inhibitory neuro

Question 72

Temporal Summation

Answer 72

Occurs when the pre neuron fires so rapidly that the EPSPs or IPSPs add up on top of each other. If they are EPSPs, the additive effect might be enough to reach the threshold depolarization required to start a postsynaptic action potential. If they r IPSPs, the postsynaptic cell may hyperpolarize, moving further and further away from the threshold as it become inhibited. Temporal summation talks about the additive effect of EPSPs which are generated from 1 synapse by a series of high frequency action potentials on the presynaptic neuron.

Question 73

Spatial summation

Answer 73

EPSPs or IPSPs from all synapses on he post are summed at any given moment in time. If the total of the sum causes the post to reach the threshold voltage, the action potential will be fired. Spatial summation is the additive effect which is created by many EPSPs which have been generated at many different synapses on the same post neuron at the same time.

Question 74

In which of the following ways can a presynaptic neuron increase the intensity of the signal it transmits?
A) Increase the size of presynaptic action potentials
B) Increase the frequency of action potentials
C) Change type of neuro it transmits
D) Change speed of action potential propogation

Answer 74

A neuron cannot change the size of action potentials it transmits, but it can increase the number of action potentials it transmits in a given amount of time ( the frequency of action potentials ) . The increase frequency of action potentials can add up thru temporal sum in the post cell to produce an increased response ( B is the answer). Action potentials are all or nothing once they r started. The magnitude of mem depolarization during propogation of the action potential does not change . A is wrong, A neuron cannot change the type of neuro it releases, C is wrong; and the speed of propogation cannot be varied from 1 action potential to the next D is wrong .

Question 75

Somatic division of PNS

Answer 75

Portion of system concerned with conscious sensation and deliberate voluntary movement of skeletal muscle.

Question 76

Autonomic division of PNS

Answer 76

Portion concerned with digestion, metabolism, circulation, perspiration and other involuntary processes.

Question 77

2 efferent portions of autonomic division

Answer 77

Sympa and parasympa

Question 78

General effects of sympa and para

Answer 78

When sympa activated, body is prepared for fight or flight; results in the release of epinephrine into the bloodstream by the adrenal medulla
When para activated , body prepared to rest and digest

Question 79

Para and sympa effect on digestive system: glands

Answer 79

para: stimulation
sympa: inhibition

Question 80

Para and sympa on digestive system: motility

Answer 80

para: stimulation ( stimulates digestion)
sympa: inhibition ( inhibits digestion)

Question 81

Para and sympa on digestive system: sphincters

Answer 81

para: relaxation
sympa: contraction

Question 82

Para and sympa on urinary system bladder

Answer 82

P: contraction ( stimulates urination)
S: relaxation (inhibits urination)

Question 83

P and S on urinary system: urethral sphincter

Answer 83

P: relaxation ( stimulates urination)
S: contraction ( inhibits urination)

Question 84

P and S on bronchial smooth muscle

Answer 84

P: constriction ( closes airways)
S: relaxation ( opens airways)

Question 85

P and S on cardio system: heart rate and contractility

Answer 85

P: decreased
S: increased

Question 86

P and S on cardio system: blood flow to skeletal muscle

Answer 86

P: -
S: increased

Question 87

P and S on skin

Answer 87

P: -
S: sweating and general vasoconstriction; emotional vasodilation ( blushing)

Question 88

P and S on eye: pupil

Answer 88

P: constriction
S: dilation

Question 89

P and S on eye: muscle controlling lens

Answer 89

P: near vision accommodation
S: accommodation for far vision

Question 90

P and S on adrenal medulla

Answer 90

P: No effect

S; Release of epinephrine

Question 91

P and S on genitals

Answer 91

P: erection/lubrication
S: ejaculation/ orgasm

Question 92

reflex

Answer 92

response to a stimulus which does not require the involvement of conciousness

Question 93

components of a reflex

Answer 93

1. afferent ( involves info about a stimulus into the CNS)

2. efferent ( carries info away from the CNS to initiate a response in the periphery

Question 94

reflexes and side of the body the efferent goes to

Answer 94

some like the muscle stretch has afferent which brings info in from 1 side of the body and efferent which brings info to that same side
others efferent comes on both sides

Question 95

descrbe how voltage gated potassium channels contribute to repolarization of the membrane

Answer 95

2) Voltage-gated K+ channels open more slowly than the voltage gated Na+ channels and stay open longer
Voltage gated K+ channels open in response to membrane depolarization. As the K+ leaves the cell dn its conc.n gradient , mem pot.l returns to negative values , actually overshooting the resting potential by about 20 mV to about -90 mV . At this pt, K+ channels close.

Question 96

describe how Na+/K+ pump contributes to the repolarization of the membrane

Answer 96

3) K+ leak channels and Na+/K+ ATPase continue to function ( as they always do) to bring the mem back to resting potential. It could do so alone but it would take a lot longer.

Question 97

name the three factors which contribute to repolarization of the membrane

Answer 97

Na+ voltage gated
K+ voltage gated
Na+/K+ pump

Question 98

list location and primary function of

Oligodendrocytes

Answer 98

Oligodendrocytes (CNS): form myelin- increase speed of conduction of action potentials along axon

Question 99

list location and primary function of

Astrocytes

Answer 99

Astrocytes ( CNS): Guide neuronal development, regulate synaptic communication via regulation of neurotransmitter levels

Question 100

list location and primary fuction of

Microglia

Answer 100

Microglia (CNS): Remove dead cells and debris

Question 101

list location and primary function of

Ependymal cells

Answer 101

Ependymal cells (CNS): Produce and circulate cerebrospinal fluid

Question 102

Ehat does the equlibrium potential of K+ regarding ion movement

Answer 102

K+ are driven outward by their concentration gradient. However, if the interior of the cell is too negative, the positively charged ions cannot escape the attraction ; the electrical gradient drive K+ in. The chemical gradient driving K+ out and the electrical gradient driving K+ in balance each other at about -90 mV, so this is the equilibrium potential for K+.

Question 103

voltage gated Na+ during absolute refractory period

Answer 103

During this time, the voltage gated Na channels have been inactivated after depolarization. They will not be able to open again until the membrane potential reaches the resting potential and the Na channels have reached their closed state. These periods help direct the action potential because only channels further downstream can open and let in the depolarizing ions.

Question 104

hyperpolarized period during relative refractory period

Answer 104

Hyperpolarized state is found in the brief period in which the membrane potential is more negative than the resting potential as a result of the voltage gated K channels which have not closed yet. Because it is further from the threshold, a greater stimulus is required to open the voltage gated Na channels to start an action potential.

Question 105

relative refractory period is the period after

Answer 105

absolute refractory period when it is really hard to send an action potential. It would take more positive ions than usual to reach appropriate depolarization potential. The initial triggering event would have to be bigger than normal to send more action potentials along.